Air-break low-voltage switching devices, such as low-voltage power breakers, require for their operation an arc-quenching device, in the form of arcing chambers for cooling and quenching arcs which occur when the contact is broken. Such an arc-quenching device is capable of quenching any arcs that occur without adversely affecting the power breaker itself and adjacent parts of the system or other assemblies, since, otherwise, there would be a risk of the hot and thus ionized arc gases causing electrical flashovers or resulting in other damage. Each arc-quenching chamber generally includes a large number of arc splitter plates, which are arranged between two side walls and contribute to the cooling and quenching of the arc. Two fundamentally different physical forms of conventional arc-quenching devices are known for low-voltage power breakers. Until now, for large power breakers, complete arcing chambers produced essentially in a conventional manner, separately as a component, i.e. a robust arc-, pressure- and temperature-resistant enclosure containing arc splitter plates and having a suitable blowing apparatus, have been fitted to the power breaker. One arcing chamber is generally provided per pole. This chamber has a complete enclosure whose strength is matched to both the mechanical and the electrical forces of the arc which occurs in it and is to be quenched, in particular with regard to the pressure and the temperature of the switching gases. The arc splitter plates are located in this chamber. The chamber may in this case be in the form of a pot-like shaft into which the plates are inserted, or may be in the form of a structure composed of half-shells, for which an apparatus is required, firstly for inserting the plates into one half-shell, then for fitting the second half-shell, and finally for connecting the two half-shells.
A second physical form makes use of arcing chamber inserts, with which only the function of actual arc quenching can be achieved in one unit. These structures are, however, not capable of withstanding the pressure occurring in connection with the arc. These inserts are therefore inserted in a shaft which is provided in or on the breaker enclosure. Until now, this physical form has predominantly been used for small, compact power breakers, but is increasingly also being used for larger power breakers where the enclosures surround these areas, i.e. the switching area and the quenching area.
With regard to the connection to the main body of the power breaker and the connection of its individual parts to one another, both types have the object of sealing the technically required gaps and joints to prevent the ionized arc gases passing through them, and of preventing electrical flashovers caused by gases which may nevertheless occur.
The arc-quenching chambers can have entirely different dimensions which are dependent on the dimensions of the entire contact system, since the arc-quenching chamber should after all accommodate the arc which runs from the contact system. In this case, low-voltage power breakers having a high rated current have, as a function of the rated or continuous current of the breaker and as a function of the operation, a very wide contact system.
The arc-quenching chamber does not necessarily have to cover the entire width, rather it is sufficient to join the arc by way of a horn and then to pass it into a relatively narrow chamber which is dimensioned such that it has the switching capacity produced by the short-circuit switching capacity of the breaker.
If, however, the contact system is wider than the arc-quenching chamber, this results in a system in which guides are provided to enable the arc to be formed from all of the arc elements which may be struck, and in which the guides guide the arc onto arcing horns which are provided and open into the chamber. Accordingly, these additional guides are necessary, which leads to additional complexity in terms of materials and assembly and to additional expense in connection with this.
It has been proven, however, that it is advantageous and expedient if the chamber is as wide as the contact system and that the arc, irrespective of whether it runs on the left, the right or in the center, runs into the arcing chamber where it can become broader. Extremely wide arc-quenching chambers are, however, deemed unfavorable to a certain extent with regard to the quenching behavior in the case of short-circuit current disconnections. The area available is therefore advantageously filled in a modular fashion using smaller inserts.
Such an arrangement is proposed in DE 197 15 116 C2 (WO 98/47161). In this case, an arcing chamber system having a chamber body is described in which a large number of grooves are arranged on the insides of two opposite side walls, and a number of arcing chamber modules, which each have two opposite side parts, between which a large number of arc splitter plates are in each case arranged, the side parts of the arcing chamber modules being inserted into the corresponding grooves in the side walls.
The grooves provided in the walls of the chamber body reduce the strength of the chamber body, and the base body must have, overall, a greater material strength. This means increased use of materials and an increased weight. A further arc-quenching arrangement is disclosed in DE 17 46 087 U1. A number of isolating profiled bodies are arranged in a retaining frame, which is formed by two flat elements and two U-shaped elements, U-shaped profiled bodies and, in between, double T-shaped profiled bodies in each case being arranged in the edge regions, such that cavities are formed between two adjacent profiled bodies. Grooves are provided on the insides of these cavities for accommodating arc splitter plates. This arrangement can be regarded as an arc-quenching chamber, but no arcing chamber modules are used and neither is there a chamber body since the profiled elements are only held together by a retaining frame.